This application claims the priority of 102 02 579.7, filed Jan. 24, 2002, the disclosure of which is expressly incorporated by reference herein.
The invention concerns a method for raising or lowering the interior pressure of a hollow body to a specified set internal pressure.
One or more hollow bodies are to be provided with various set internal pressures. These set pressures can be different and/or vary over time. As an example, if the hollow bodies are part of a comfort system in a motor vehicle, for example, a system with pneumatically adjustable seats, then the set pressures depend upon the wish of the occupants. The hollow bodies are, moreover, not only to be brought to specified internal pressures in a short time. In addition, a reduction in passenger comfort level with a sudden change in pressure noticeable to the occupants should be avoided. Furthermore, adjusting the set pressures should require as few sensors and as few pressure measurements as possible.
A method for filling hollow bodies with the aid of a pressure generator is known from German Reference DE 3804959 C2. The application is disclosed that the hollow body is a set of air chambers of a seat, for example, of a motor vehicle, that the pressure generator includes a pump. After measuring the actual internal pressure of one of the hollow bodies, its internal pressure is first rapidly brought to a value near a specified set internal pressure. When a ventilation valve is closed, the actual internal pressure obtained is compared with the set internal pressure and pressure is applied again in the event of a deviation. Pressure is preferably administered with a diminished filling rate after the first comparison, for example, by a pump with reduced rotational speed or a ventilation valve with diminished through flow.
The method disclosed in German Reference DE 3804959 C2 can lead to a noticeable, indeed jerky, change in pressure, for example, in the case of a motor vehicle seat, especially with a large deviation between set and actual internal pressure. This change in pressure is felt to be a restriction in sitting comfort precisely when the approximate set internal pressure is reached, and under certain circumstances, the seat occupant is even frightened or irritated. The advantageous configuration described above, moreover, requires extra or expensive apparatus, for example, various valves or a controllable pump.
A pressure supply facility for at least two users is known from German Reference DE 4210049 C1. At least two users are to be provided with two different nominal pressures. One pressure generator is to be activated so that it supplies each of the two required nominal pressures. The facility accomplishes the objective, certain to prevent the user with the lower pressure from being acted upon with the higher nominal pressure. This is attained with a protective circuit in which certain switch settings can only be reached at certain levels of pressure. How to avoid a rapid change in pressure while supplying pressure and how an overshot of the pressure curve is avoided are not disclosed.
A method for driving stability control switching with control through pressure gradients is disclosed in German Reference DE 19515050 A1. A regulating unit receives a reference speed Vref and a steering angle xcex4 as input magnitudes. The angle of yaw g and the angle of yaw rate P are regulated, among other things. Pressure p in the wheel brakes is a manipulated variable. The absolute pressure is not specified, but rather pressure alteration signals that prescribe whether the pressure should be increased or diminished on individual wheel brakes. The change in pressure depends upon the measured magnitudes of the motor vehicle, for example, a required additional yaw factor. In order to determine the change in pressure, sensors are needed not only for the pressure, but also for further magnitudes.
The invention is based upon the objective of creating a method of the type mentioned at the beginning that avoids the disadvantages of the state of the art. In particular, abrupt or major changes in pressure are to be avoided and the method should manage with as few sensors and as few pressure measurements as possible.
In order to raise the internal pressure of a hollow body to a specified set internal pressure with a specified tolerance, a pressure generator connected with the hollow body is used. The actual internal pressure of the hollow body is determined before the elevation. Several pressure-raising steps are conducted in accordance with the invention. For each pressure-elevating step, the internal pressure of the hollow body is raised, on the one hand, by an amount that is smaller or equal to a specified upper limit for a pressure elevation in a hollow body. On the other hand, the amount of the pressure increase brought about by the pressure-raising step is calculated. Conducting these pressure elevation steps is broken off as soon as the sum on the basis of the actual internal pressure before the increase and the amounts of all previously conducted pressure elevations deviates from the set internal pressure by at most the specified tolerance.
In order to reduce the internal pressure of a hollow body to a specified set internal pressure with a specified tolerance, the hollow body is joined with a connection with the environment which has a lower pressure than the set internal pressure. The actual internal pressure is ascertained before the reduction. Several pressure-reducing steps are conducted in accordance with the invention. For each pressure reduction step, the internal pressure of the hollow body is diminished by the pressure decreasing step by an amount which is smaller or equal to a specified upper limit for a pressure reduction in the hollow body on the one hand. On the other hand, the amount of the pressure reduction brought about by the pressure-reducing step is determined. Conducting these pressure reduction steps is stopped as soon as the sum of the actual internal pressure prior to the reduction and the amounts of all previously conducted pressure reductions deviates from the set internal pressure by at most the specified tolerance.
A device for conducting the method of the invention for raising pressure includes,
a pressure generator, a supply line between pressure generator, hollow body and environment, a sensor for measuring the internal pressure of the supply line, and a control device for conducting the pressure-increasing steps.
A device for conducting the method of the invention for reducing pressure includes,
a supply line between pressure generator, hollow body and environment, a sensor for measuring the internal pressure of the supply line, and a control device for conducting the pressure-reducing steps.
The set internal pressure of the hollow body is slowly moved in several steps through the method. The upper limit of a pressure increase or pressure reduction is specified such that the respective requirements, for example as to comfort, are fulfilled. In this way, for example, an occupant of a passenger vehicle or a traveler on a bus does not observe any disturbing jerking owing to pressure changes in adjusting his/her seat, which is brought into a desired position in that the set internal pressures of hollow bodies in the seat are brought to specified values in accordance with the invention.
Overshooting the pressure curve is avoided by the method of the invention, thus temporarily assuming a value above the set internal pressure with a pressure increase and temporarily a value beneath the set internal pressure with a pressure reduction.
The method saves sensors and measurement processes. The actual internal pressure of the hollow body is measured once before the beginning of the change in pressure, which requires a sensor. Furthermore, the amounts of the increases in pressure or the pressure reductions are ascertained. In the event of a pressure increase, these amounts depend upon the pressure which the pressure generator generates, as well as according to the time span in which the pressure of the pressure generator applies to the hollow body, and/or upon the volume of the hollow body as well as on the supply line between pressure generator and hollow body. In the case of a reduction in pressure, these amounts depend, according to configuration of the time span in which the pressure of the pressure generator applies on the hollow body, and/or upon the volume of the hollow body as well as on that of a pressure line between pressure generator and hollow body. It is not necessary to measure the actual internal pressure of the hollow body during a pressure change again.
In accordance with one embodiment, at least one pressure-raising step is conducted through three increments.
In the first of these increments, a second valve and a further valve are closed and subsequently a first valve is opened. The second valve is situated between the pressure generator and a supply line which joins the pressure generator with the hollow body. The additional valve is situated between the hollow body and the supply line. The first valve is situated between the supply line and a connection with the environment.
In the following second increment, the first valve is closed and the second valve is opened. In the subsequent third increment, the second valve is closed and the additional valve is opened.
An advantageous configuration of these increments uses a first increment which is conducted at least until the internal pressure in the supply line is equal to ambient pressure. During a second increment, a constant pressure is generated by the pressure generator.
The second increment is conducted at least until the internal pressure in the supply line is equal to the pressure generated by the pressure generator. The third increment is conducted at least until the supply line and the hollow body have the same internal pressure.
This configuration saves monitoring the time span in which the first valve is opened between the supply line and the hollow body. It suffices if the first valve is opened until the actual internal pressures of the hollow body and supply line agree with sufficient exactitude. Here, it is sufficient for an immediate determination of the lower limit for this time span, which suffices for all practical internal pressures of the hollow body and the supply line. This time span comes to 0.5 sec, for example, with a seat system.
In another embodiment, the second increment is ended after a previously determined time span. The third increment is carried out until the supply line and the hollow body have the same internal pressure.
A further embodiment provides that the second increment is carried out at least until the internal pressure in the supply line is equal to the pressure generated by the pressure generator. The third increment is concluded following the expiration of a certain time span.
In many situations, the configurations require less time than other configurations because it is not necessary to wait until an identical internal pressure has occurred.
A method to determine the amount of pressure generated by the pressure generator according to the present invention is based on the volume of the hollow body, the volume of the supply line, the total on the basis of the actual internal pressure and the amounts of all previously conducted pressure-increasing steps, and the specified upper limit for a pressure elevation in the hollow body.
One configuration of the present invention is applicable for the case in which the pressure generator is connected with several hollow bodies. In accordance with the invention, pressure-increasing steps are conducted for several of these hollow bodies in an alternating manner.
A method for measuring the actual internal pressure of each hollow body by approximation prior to the increase by using a first valve is situated between the supply line and a connection with the environment, a second valve is situated between the pressure generator and a supply line which joins the pressure generator with the hollow body, and additional valves are situated between a hollow body and the supply line in each case.
The following steps are conducted for each hollow body successively:
The pressure in the supply line is reduced by closing the second valve, by closing the additional valve and by opening the first valve to ambient pressure.
Subsequently the first valve is closed and the additional valve for this hollow body is opened at least until the same internal pressure appears in the supply line and the hollow body.
The internal pressure which arises in the supply line is measured by a sensor on the supply line.
Analogously advantageous configurations provide for reducing the pressure.
In one configuration, at least one pressure reduction step is conducted through two increments. In the first of these increments, an additional valve and a first valve are opened. The additional valve is situated between the hollow body and the connection line. The first valve is situated between the environment and a connection line that joins the hollow body with the environment. In the subsequent increment, the first valve is closed and the additional valve is opened.
In another configuration, the first increment is conducted at least until the internal pressure in the supply line is equal to ambient pressure. The second increment is conducted at least until the internal pressure in the hollow body is equal to the internal pressure in the connection line.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.